Thermostatic circuit breaker



June 28, i 93 2,

THERMOSTATIC CEIRCLEJI Filed Nov 1'7, 2 Sheets-Sheet l NE 1932- T. WHiTEFORD ET AL 3 3 THERMOS TAT IC C TRCUIT BREAKER Filed Nov. 17, 1930 2 Sheets-$heet 2 Patented 28.1932

I msscnusnr'rs g TBEBKOSTATIG cmcurr mama Appllcatlon'flled November 17, 1980. Serial 170.4%,106.

The principal object of our invention is to do away with the nec ssity of a fuse by permitting the movement of a switch member out of bridging position in the event of a short I circuit, it being new withus to provide a thermal member acting under the influence of electric current to control the opening movement of a switch member.

' A feature of our invention is a thermal elel ment which, under short circuit conditions,

moves to permit breaking of the normal circuit and, after such movement returns, after Y cooling, to former normal position. In the referred form we provide resetting means 15 or the switch member.

Another feature is a special form of thermal member.

Another feature is the normally relative freedom from pressure between the thermal member and the member which it latches.

Another feature is a special form of knob. Other features will be pointed out below. Figure 1 is a central vertical section of a device embodying our invention;

Figure 2 is an enlarged bottom perspective of the supporting disk and parts carried by Figure 3 is an'enlar ed top plan of said su orting disk and the? parts carried b it; igure 4 is a side elevation of the ob described below, I

Figure 5 is an end elevation of said knob looking in the direction .of the arrow in Figure 4; and i Figures 6 and 7 and 8 are details described below.

Supporti disk 1 has In 2'entering recesses 3 (see igure 6) in cy 'ndrical member 4 to prevent rotation of said disk, the latter being of suitable insulating material, such as porcelain, and is externally threaded to engage metal shell 5. Insulating casing 4 supports metal terminal 6 and is made in two parts as described below.

N on-conducting member 7, such as fibre, is held to the bottom of member 1 by rivet 8 which holds thermal metal element 9 in place and also holds switch clip 10 in place. Rivet 11 aids in holding element 9 and non-conducting member 7 against undesired movement.

below. A i V v Element 9 comprises two metals, preferably brass and invar, the coefiicient of expansrarss PATENT orrica I 1"? want-roan, or causes, m nawnnnca n. nomrmn or Eva'am'r,

Upon member 7 is pivotally mounted arm 12 sloted at 13 sion of one metal, such as brass in the preferred form, being to receive the pin referred to s5 greater than the other, causing element 9 to bend downward under the influence of heat, the brass being above the invar. Element 9 is slotted at 14 so that the.

current enters at leg 15, passes around slot 14 and out at leg 16, these legs being integral with element 9.

On the top of disk 1 are mounted switch.

clip 10 and switch clip 17 the current entering clip 10 from rivet 8 holding le 16 and leaving through clip 17 which is he d to the disk 1 by rivet 18, which also holds conducting strip 19 bent to pass through insulating member 4 into electrical contact with metal shell 5. Rivet 11, as shown in Figure 7, is electrically connected with strip 20 which is of fusible material, such as lead, which will melt and break the circuit at a predetermined temperature caused by the current and above the operating temperature of the thermal member 9, said strip being operative in case the thermal member, under some abnormal condition, should fail to operate properly. Sti'ip 20 is in electrical contact with termina 6. a

Knob 22 is of molded insulating material, such as bakelite, and has integral circular shoulder 23 and integral hexagonal shoulder 24 and integral circular shoulder 25-.

lVhile knob 22 is being molded hexagonal metal member 26 is inserted therein. Shoulproper spacing of knob 22 which engages hexmovement of member close to t and consequently for knob 22, the latter being held properly in relation to disk 1 by the heading over of the bottom of metal member 26. Between said headed over portion and the disk 1 is located metal arm 30 which has an interior hexagonal recess to operatively engage the lower part of hexagonal metal member 26, so that said arm 30 will rotate in fixed relation to knob 22. Arm 30 carries pin 31 made by bending a small integral portion of the metal, pin 31 riding in slot 13.

Normally the parts are'as shown in full lines in Figures 2 and 3, the arm 12 being latched under the S10 ed hook or catch portion 32 of member 9. hen a short circuit or excessive amount of current passes through member 9, the latter bends downward due to the thermal qualities above described which immediately releases slotted arm 12 and consequently, through pin 31, allows spring 27 to act to move the switch member 261 out of contact with the switch clips to break the circuit with a very quick break or snap to avoid arcing. In Figures 2 and 3 various elements are shown in dotted'lines to indicate their positions when the circuit is broken. When it is desired to reset the switch the knob is turned clockwise and the pin rides in the slot 13 and moves arm 12 back into normal latched position under hook or catch 32, member 9 moving downward sufiiciently to permit such latching. Member 9 bends downward as above described by reason of a short circuit or excessive heat, but, after cooling due to the breaking of the circuit, which cooling occurs almost immediately, returns upwardly to nor-- real or latching position.

Pin 31, at the time of latching, is subject to the full lpressure of spring 21, and is very e pivot of arm 12 and consequently the free end of arm 12, due to said relation to said pivot, has a very small pressure against the hook of thermal member 9, this being very advantageous because it permits very easy 9 to permit desired unlatching, as, perage, and also permits the thermal member to return to normal position after being subjected to an overload of current not suiiicient to break the circuit.

Spring 27 is designed so that when the switch is closed the maximum spring pressure is exerted on switch member 261, but when the switch snaps open, coming to a stop when pin 31 hits against the end of slot 13, (shown dotted inFig. 2 the tension of the spring is greatly reduce allowing pin 31 to be stopped abruptly but without sufiicient force to affect wearing of the parts.

Cylindrical molded member 4 is molded in two halves and assembled by clamping the halves around disk 1, the assembly being held together by metal shell 5 which is screwed on and secured by crimping, for example, said two halves being shown in Figure 8 which is for example, at the desired amaccuse a section of line 8-8 of Figure 1 on a smaller scale.

What we claim is:

1. A device of the character described comprising conducting terminals; a switch member normally bridging said terminals; 0. thermal member; a pivoted member normally held against movement by said thermal member; means tending normally to move said switch member out of bridging position; an element separate from said pivoted member and having operative connection with relation to said switch member and having a a portion to operatively engage said pivoted member, the point of such engagement being normally very close to the pivot of said pivoted member, whereby the thermal member is allowed to return to normal position after being subjected to an overload of current not sufiicient to break the circuit.

2. A device of the character described comprising a disk carrying terminals at one face; a resetting knob mounted to rotate on said disk and carrying a switch member normally bridging said terminals; a spring around said knob and mounted so as to ten to move said switch member out of bridging position; a pivoted member mounted at the other face of said disk and having fixed connection with said knob, said pivoted member carrying a pin; a second pivoted member mounted at said other face of said disk and having a slot within which said pin rides; and a thermal member mounted on said other face and normally latching said slotted pivoted member against movement.

THOMAS WHITEFORD. V LAWRENCE E. D ONNELL.

Ill 

